Allen revealed last week that he has been troubled by a shoulder problem for several years, and that it has started to get worse since last October.

The 23-year-old has been playing on through the injury, but Liverpool manager Brendan Rodgers has confirmed that an operation is needed to sort it out. Any surgery would keep the midfielder out of action for three months, and the Wales international is keen to get it done sooner rather than later so that he can be ready for the start of next season.

Allen was named in the starting line-up for Saturday's 3-1 Premier League defeat at Southampton, but came off at half-time.

The former Swansea man's withdrawal from international duty is a blow to Wales manager Chris Coleman, who had expected the midfielder to play a part against Scotland at Hampden Park this Friday night.

Defeat at Southampton was a major setback to Liverpool's chances of qualifying for Europe, but Jordan Henderson has not given up hope.

Henderson believes Rodgers' side, who are seventh, can close the five-point gap between themselves and fifth-placed Arsenal to reach next season's Europa League.

"It was a big disappointment against Southampton but Europe's not gone yet," he told the Liverpool Echo.

"We've still got eight games to play and that's a lot of points to play for. We've still got to play some of the teams above us so we have to keep going.

"We have to pick ourselves up from this and ensure we respond positively against Aston Villa after the international break."